The role of the Molecular Genetics Core in this project is to provide technical assistance to projects #2 and #3, as well as generate a molecular genetics database to be shared with all the components of this program project. The assistance will involve candidate gene direct sequencing, mouse mapping and genotyping and candidate gene LOH analysis of systemic regions of human chromosomes for Project 2 of the for Project 2. Assistance for Project 3 will involve the analysis of microsatellite instability and sequencing of mismatch repair genes hMSH2 and hMLH1 [when necessary hMSH3, hMSH6 and hPMS2], sequencing of mismatch repair genes hMSH2 and hMSH2 and hMLH1[ when necessary hMSH3, hMSH6 and hPMS2], and sequencing of exons 5-9 of p53 gene and sequencing of codons 12/13 and 61 in the K-ras gene in rectal carcinoma samples. In addition, simple repeat sequences in the coding regions of the Transforming Growth Factor-b1 Type II Receptor (TGF-b1RII), the Insulin-Like Growth Factor II Receptor (IGFII2), BAX, b-catenin and Tcf-4 will be examined to analyze MMR-Pathway and Aneuploid- Pathway alterations present in the tumor samples. The Core contains state of the art molecular biology equipment, including two Applied Biosystems 3948 nucleic acid synthesis and purification systems (48 column capacity each), six Applied Biosystems Prism 377 DNA sequencers. Primary data, analyzed with the assistance of our Shared Computer Facility, will be provided to Principal Investigators of the other projects in clearly understandable formats. Because different steps are involved in the generation of primary data, results will be verified together with other Principal Investigators to eliminate any source of potential errors. By providing primary data concerning the indicated genetic analysis, the Molecular Genetics Core will allow to correlate genetic and clinico-pathological data, thereby giving the opportunity to examine the role of these genes in rectal tumorigenesis. Interaction of the Molecular Genetics Core with all the components involved in this project is a necessary element for the fulfillment of the primary objectives set for the project in its entirety.